Control circuit for ac motor

ABSTRACT

A control circuit is employed to stop a tufting machine with its needles up and clear of the carpet. The AC motors, which drive the needle bar through a drive shaft connected to the motors, are disconnected from the power source when the drive shaft of the tufting machine is at a preset or selected position. After this position of the drive shaft is determined, the circuit has means to count a selected number of revolutions of the drive shaft and to then cause a DC voltage to be applied to the motors to dynamically brake the motor. As a result, the needles are positioned up and clear of the carpet when the motors are stopped.

United States Patent [1 1 Owens 3,494,312 2/1970 Kubokura et a1. 318/212 X [451 Aug. 14, 1973 3,617,837 11/1971 Beck ..318/212 Primary Examiner-Gene Z. Rubinson Attorney-Lamont Johnston 57-] ABSTRACT A control circuit is employed to stop a tufting machine with its needles up and clear of the carpet. The AC motors, which drive the needle bar through a drive shaft connected to the motors, are disconnected from the power source when the drive shaft of the tufting machine is at a preset or selected position. After this position of the drive shaft is determined, the circuit has means to count 21 selected number of revolutions of the drive shaft and to then cause a DC voltage to be applied to the motors to dynamically brake the motor. As a result, the needles are positioned up and clear of the carpet when the motors are stopped.

3 Claims, 2 Drawing Figures 22 2e 25 0d 20 1,1 L k MOTOR O 24/ 25'2 1|L25 3 263x] 26 21 MOTOR OCQZG 5 ,51 5o 40 2e-2 26-4 .512% .aiii. "*i 05 \J P139 i; PILOT LIGHT J 159 o1o 84 o11 83 012 CONTROL CIRCUIT FOR AC MOTOR In a tufting machine, the needle bar and the loopers are driven from a motive source which may be either AC or DC motors. For example, one or two AC motors with each having about ten horsepower may be used to drive the needle bar and the loopers.

When AC motors are employed, one means of stopping the driving of the needle bar and the loopers has been to utilize a mechanical disc brake, which is held disengaged when AC power is supplied to the motors. When the AC power is disconnected, a holding solenoid, which holds the mechanical disc brake disengaged, is deenergized so that the disc brake becomes effective.

While this type of braking arrangement is effective, it has two distinct disadvantages. One is that the life of the disc brake is very short, namely, about 4 to 6 months, so that the tufting machine must be inactivated to enable replacement of the disc brake. Of course, this increases production costs due to the down time of the tufting machine and the labor and material to replace the disc brake.

Another disadvantage is that the holding solenoid becomes weak so that the brake is effective while the motors are running. Before it is recognized that the disc brake iseffective while the motors are running, the motors usually overload and burn up. This also adds substantially to production costs.

In addition to using a mechanical disc brake for stopping the drive of a tufting machine, it also has previously been suggested to utilize a clutch to disengage the drive shaft of the tufting machine from the motor or motors. However, this arrangement still requires some type of mechanical braking arrangement to brake the drive shaft of the tufting machine.

The present invention satisfactorily solves the foregoing problems by providing a control circuit in which braking of an AC motor or motors of a tufting machine is accomplished without any additional mechanical components 'and is moreeffective than a mechanical disc brake. The present invention employs a dynamic braking system wherein DC current is applied to a winding of each of the AC motors to stop the motors.

Furthermore, in a tufting machine, it is desired to be able to stop the drive so that the needles, which are carried by the needle bar, are in an up position so as to be clear of the carpet and the loopers are withdrawn from the loops. This prevents yarn tension when the tufting machine is stopped.

The present invention satisfactorily meets this problem by enabling the tufting machine to be stopped with the needles up and clear of the carpet and the loopers withdrawn from the loops. The control circuit of the present invention senses when the drive shaft of the tufting machine is in a preset or selected rotary position and then stops the tufting machine a predetermined number of revolutions of the drive shaft after sensing the selected position of the drive shaft.

An object of this invention is to provide a device for controlling stopping of an AC motor having a constant load.

This invention relates to a device for automatically stopping an AC motor having a constant load at a predetermined rotary position. The device includes means to sense when the motor is at a selected rotary position, means to produce a signal when it isdesired to stop the motor, means to disconnect the motor from its AC power source in response to 'a signal from the producing means and the sensing means sensing that the motor is at the selected rotary position, and means to apply a DC voltage to the motor a predetermined period of time after the disconnecting means is effective to dynamically brake the motor so that the motor stops at the predetermined rotary position. v

The attached drawings illustrate a preferred embodiment of the invention, in which:

FIG. 1 is a wiring diagram of a portion of the control circuit of the present invention; and

FIG. 2 is a wiring diagram of the remainder of the control circuit of the present invention.

Referring to the drawings and particularly FIG. 1, there are shown AC induction motors 20 and 21 for driving a needle bar and loopers of a tufting machine through a common drive shaft in the well-known manner. The motors 20 and 21 are connected to a three phase AC source (not shown) through leads 22, 23 and 24 whenever normally open contacts 25-1, 25-2, and 25-3 of an AC control relay 25 are closed. Between the normally open contacts 25-1 and 25-3 of the control relay 25 and the motors 20 and 21, there are disposed overload circuit breakers 26.

It should be understood that power is turned on through closing a main disconnect switch (not shown) whereby the leads 22, 23 and 24 are connected to the AC power source. However, the motors 20 and 21 cannot be energized unless the control relay 25 is picked up. Thus, by the relay 25 not being energized, the mo tors 20 and 21 are turned off even though power is supplied through the leads 22, 23 and 24 due to the main disconnect switch being closed.

Even if the control relay 25 is picked up, an overload causes the overload circuit breakers 26, which are heaters, to heat sufficiently to result in their normally closed contacts 26-1, 26-2, 26-3 and 26-4 opening. This causes deenergization of the control relay 25 so that the contacts 25-1, 25-2 and 25-3 of the control relay 25 open to stop the motors 20 and 21.

One side of the control relay 25 is connected through the overload contacts 26-1, 26-2, 26.-3 and 26-4 and a lead 27 to one side of a secondary winding 28 of a transformer 29. The transformer 29 has its primary winding 30 connected through leads 31 and 32 to the power supply leads 23 and 24, respectively.

The other side of the secondary winding 28 of the transformer 29 is connected through a lead 33, which has an emergency stop push button 34 therein, to terminal 1 of a terminal board 35. The terminal board 35 has terminals 1 to 12 with one of each of terminals 1 to 12 being shown on the terminal board 35 and the other of each of tenninals 1 to 12 of the terminal board 35 being shown schematically in FIG. 2 by the number of the terminal being encircled.

Terminal 1 of the terminal board 35 also is connected to one side of a primary winding 36 (see FIG. 2) of a transformer 37. The primary winding 36 has its other side connected through terminal 2 of the terminal board 35 and a lead 38 (see FIG. 1) to the lead 27. Accordingly, power is always provided through terminals l and 2 of the terminal board 35 to the transformer 37 whenever the leads 22, 23 and 24 are connected to the power source.

The other side of the control relay 25 is connected through terminal 3 of the terminal board 35, normally open contacts 39-1 (see FIG. 2) of a DC control relay 39, and a lead 40 to terminal 1 of the terminal board 35. Thus, the control relay 25 can be energized to allow the motors and 21 to be activated only when the control relay 39 is picked up so that its normally open contacts 39-1 are closed.

One side of the control relay 39 is connected through normally closed contacts 41-1 of a DC control relay 41 to a lead 42, which is connected to the positive side of a bridge rectifier 43 supplying a DC voltage of approximately volts RMS. The voltage is supplied from the transformer 37 by its secondard winding 44 to the bridge rectifier 43. The negative side of the bridge rectifier 43 is connected to ground by a lead 45.

The other side of the control relay 39 is connected through an NPN transistor 46 to ground. Thus, the relay 39 can be activated only when the transistor 46 is turned on and the control relay 41 is deenergized.

The control relay 41 also is connected to the lead 42 through normally closed contacts 39-2 of the control relay 39. The control relay 41 can be energized only when it is connected to ground through an NPN transistor 47 being saturated and the controlrelay 39is inactivated.

Thus, neither of the relays 39 and 41 can be pickedup if the other is already energized. The activation of each of the relays 39 and 41 is controlled by the circuit of the present invention.

The unfiltered DC voltage from the lead 42 also is supplied through a diode 48 to tenninal 7 of the terminal board and to a capacitor 49, which charges to approximately 36 volts. The charged voltage from the capacitor 49 is supplied through terminal 7 of the terminal board 35 to power a proximity sensor, which includes a sensor amplifier 50 (see FIG. 1) and a sensor head 51. The sensor amplifier 50 is connected to ground through terminal 5 of the terminal board 35 and toa capacitor 52 through terminal 6 of the terminal board 35. One suitable exampleof the proximity sensor is sold by General Electric as Model No. CR1l5D3B.

The sensor head 51 is located in thetufting machine in a position adjacent to the drive shaft of the tufting machine. The drive shaft of the tufting machine has a non-metallic disc, which has a small piece of metal secured near its circumference and flush with its surface, secured thereto. The disc is adjustable on the shaft so as to indicate to the proximity sensor a preset or selected position of the drive shaft. Whenever the drive shaft is in this preset or selected position, the sensor head 51 senses th presence of the metal in the nonmetallic disc and transmits a negative going signal to terminal 8 of the terminal board 35.

As shown in FIG. 2, the secondary winding 44 of the transformer 37 is center tapped and connected through a diode to charge a capacitor 61 to 18 volts. This DC filtered voltage is connected through a lead 62, which has a resistor 63 therein, to a Zener diode 64, which has a break down voltage of about 5.1 volts. Accordingly, the Zener diode 64 provides a DC voltage of approximately 5 volts through a lead 65 to the logic circuitry of the present invention. A capacitor 66, which is parallel to the Zener diode 64, further filters the voltage and is charged very quickly to its voltage of 5 volts.

A capacitor 67 ,which has one plate connected to the lead 65 and its other plate connected through resistors 68 and 69 to ground, has no charge when'power is applied and charges much slower than the capacitor 66 through the resistors 68 and 69. Accordingly, the junction between the resistors 68 and 69 initially goes to a positive voltage and then gradually falls to zero as the capacitor 67 charges when AC power is initially applied by closing the main disconnect switch.

This momentary positive level of the voltage between the resistors 68 and 69 is connected to bases of NPN transistors 70 and 71 through resistors 72 and 73, respectively. The positive potential at the bases of the transistors 70 and-71 turns on the transistors 70. and 71 so that current flows from thelead 65 through a resistor 74 to the collector of the transistor 70 and through a resistor 75 to the collector of the transistor 71. As a result of the voltage drop across the resistors 74 and 75 due to current flowing through the transistors 70 and I 71, respectively, the potential at the collectors of the transistors 70 and 71 falls to near 0 volts or a logical 0 (hereinafter referred to as 0).

TheO signal from the collector of the transistor 70 is connected through a lead 76 to reset (RD) input of a dual JK master slave flip flop circuit 77. This resets the flip flop ircuit 77 so that its output Q goes to 0 and its output Q goes to logical l (hereinafter referred to as l).

The collector of the transistor 71 is connected through a lead 78 to reset (RD) input of each of flip flop circuits 79, and 81. The 0 signal from the collector of the transistor 71 resets the flip flop circuits 79, 80 and 81 so that output Q of eacluaf the flip flop circuits 79, 80 and 81 is 0 and outputQ of each of the flip flop circuits 79, 80 and 81 is 1. Each of the flip flop circuits 79, 80 and 81 is adual JK master'slave flip flop circuit.

The flipflop circuits 77 and 79 are preferably an integrated circuit sold as Model US 7476A by Sprague while the flip 'flo p circuits 80 and8l are preferably an integrated circuit sold by Spragueas Model US 7473. It should be understood that it is not necessary that the flip flop circuits be integrated circuits of this specific type to perform the logic since each could be a separate flip flop circuit as long as they function in the same manner.

- Each of the flip flop circuits 77, 79, 80 and 81 is of the type in which a 0 at its reset (RD) input causes its output Q to go to 0 and its output Qto go to 1. Whenever input C of the flip flop circuit goes from 0 to 1 due to receiving a l, the information on J and K inputs is stored or latched in the flip flop circuit; then, when input C receives a 0 so as to go from 1 to 0, outputs Q and Q may change state depending on the signals 'at inputsJ and K since the stogad information is now transmitted to outputs Q and Q. When each of J and K inputs is at l and input C receives a l and then a 0,, outputs Q and 6 change state when input C receives the 0. When K is l and J is 0 and inpu t C receives a l and then a 0, output 0 is 0 and output Q is 1 when input C receives the 0. When input J is l and input K is 0 and input C receives a l and then a 0, output Q is 1 and output Q is 0 when input C receives the 0.

Each of the flip flop circuits 77 and 79 also has a set (SD) input. When set (SD) input goes to 0, output Q is l and output 6 is 0 irrespective of the signals on inputs J and K. When set (SD) input goes to 1, it has no effect on outputs Q and C Accordingly, whenever power is applied to the tufting machine through closing the main disconnect switch, all of the flip flop circuits 77 and 79-81 are steered to a reset condition so that all outputs are quiescent and the logic circuitry is ready to accept the command inputs depending on whether a start push button 82 (see FIG. 1) or a jog push button 83 is closed by the operator. When the start push button 92 is closed, terminal 19 of the terminal board 35 is connected to ground through normally closed stop push button 84 and terminal 9 of the terminal board 35. When the jog push button 83 is closed, terminal 11 of the terminal board 35 is connected to ground through the closed stop push button 84 and terminal 9 of the terminal board 35.

When the start push button 82 is closed, terminal is connected to ground so that its signal goes to 0 from 1. This 0 signal is passed through a filter network of an inductance 85 (see FIG. 2) and capacitors 86 and 87, which are in'parallel with a resistor 89 to assure that the (SD) input of flip flop circuit 77 goes to logic 1 leven when the button is not pressed, and a lead 88 to set (SD) input of the flip flop circuit 77. As a result of the 0 signal being supplied to set (SD) input of the flip flop circuit 77, the flip flop circuit 77 changes state so that its output Q goes to l and its output 6 goes to 0 irrespective of signals at inputs J and K of the flip flop circuit 77.

The flip flop circuit 77 has its output Q connected by a lead 90 to an input pin 91 of a NOR gate 92.'Accordingly, since the input pin 91 of the NOR gate 92 is at 1, output pin 93 of the NOR gate 92 is at 0. This is because the NOR gate 92 has an output of O on its output pin 93 unless inputs at both the input pin 91 and an input pin 94 are 0. When both inputs to the NOR gate 92 are at 0, the output pin 93 of the NOR gate 92 is at 1. All of the other NOR gates of the circuit of the present invention also have this logic.

The output pin 93 of the NOR gate 92 is connected to input pins 95 and 96 of a NOR'gate 97. Since both of the input pins 95 and 96 are at 0, the NOR gate 97 has its output pin 93, which is connected by a lead 99 to the base of the transistor 46 through a resistor 109, at 1. With the output pin 98 of the NOR gate 97 at 1, a positive signal is applied to the base of the transistor 46 to turn it on.

Since the output pin 98 of the NOR gate 97 also is connected by a lead 99' to input pin 191 of a NOR gate 102 so that the input pin 19!! is at l, the NOR gate 192 has its output pin 193 at 0 irrespective of the signal at its input pin 194. The output pin 193 of the NOR gate 102 is connected by a lead 195 to the base of the transistor 47 through a resistor 196. Because of the low signal at the base of the transistor 47, the transistor 47 is not tumed'on so that the control relay 41 could not be energized at this time. Accordingly, since the control relay 41 is not energized, its normally closed contacts 41-] are closed so that the control relay 39 is energized when the start push button 82 is closed.

The energization of the control relay 39 caused its normally open contacts 39 to close whereby the relay 25 (see FIG. 1) is picked. As a result, the normally open contacts 25-1, 25-2 and 25-3 of the relay 25 are closed so that the motors 20 and 21 are energized to drive the needle bar and the loopers.

When the control relay 39 is energized, its normally closed contacts 39-2 (see FIG. 2) open. Thus, the control relay 41 cannot be turned on even if the signal from the output pin 103 of the NOR gate 102 should accidentally change to 1 until the control relay 39 is turned off.

After the tufting machine has been started by closing the start push button 82, the start push button 82 can be released and the tufting machine will continue to run. This is because outputs Q and 6 of the flip flop circuit 77 will not change states when the signal on the lead 88 changes to 1 from 0.

Thus, the tufting machine continues to run until the stop push button 83 is opened. When this occurs, terminal 12 of the terminal board 35 is disconnected from ground whereby the signal on input pin 107 (see FIG. 2) of a NAND gate 108 goes to 1 since it is connected through a resistor 109 to the lead 65 from which the filtered voltage of 5 volts is applied. Whenever the stop push button 84 is closed, the 0 signal is applied through a filter network of an inductance 1110 and capacitors 111 and 112, which are grounded, to the input pin 197 of the NAND gate 198.

The NAND gate 198 has its other input pin 1 13 connected by a lead 113 and the lead to output Q of the flip flop circuit 77. Output Q does not change state after the start push button 82 is released to open even though input K of the flip flop circuit 77 is at 1 because there is no signal at input C, which is connected to output 6 of the flip flop circuit 81, of the flip flop circuit 77 due to inputs J and K of the flip flop circuit 81 being at 0 at this time. Thus, the input pin 113 of the NAND gate 108 is at 1.

Since both of the input pins 107 and 113 of the NAND gate 198 are at 1 when the stop push button 84 is opened, output pin 114 of the NAND gate 198 goes to 0 since both inputs are at l. The output pin 114 of the NAND gate 103 is at 1 except when both of the input pins 197-and 113 are at 1. All of the other NAND gates of the circuit of the present invention also have this logic.

The output pin 114 of the NAND gate 198 is connected to an input pin 115 of a NAND gate 116. Because of the input pin 1 15 of the NAND gate 116 going to 0 when the output pin 1141 of the NAND gate 108 goes to 0, output pin 117 of the NAND gate 116 goes to l irrespective of the input at input pin 118 of the NAND gate 116.

The output pin 117 of the NAND gate 116 is held at 1 even if the stop push button 84 is released to close. This is accomplished through cooperation with a NAND gate 119, which has its inputpin 120 connected to the output pin 117 of the NAND gate 116 and its output pin 121 connected to the input pin 118 of the NAND gate 116.

Since the NAND gate 119 has its input pin 122 connected to the lead 78, the output pin 121 of the NAND gate 119 goes to 0 when the output pin 117 of the NAND gate 196 goes to 1. This is because the input pin 122 of the NAND gate 119 also is at 1 since the capacitor 67 charged sufficiently to cut off the transistors 79 and 71 after a predetermined period of time whereby the signals on both of the leads 76 and 78 went to 1.

Therefore, when the signal from the output pin 1M of the NAND gate 198 goes to 1 due to the stop push button 84 being released so that the input pin 107 of the NAND gate 108 is at 0, the output pin 117 of the NAND gate 116 is held at 1 due to the NAND gate 119. Thus, a hold circuit is provided to maintain the output pm 117 of the NAND gate 116 at 1 so that it is not necessary to hold the stop push button 84 open.

The output pin 117 of the NAND gate 116 is connected by a lead 123 to inputs J and K of the flip flop circuit 81. Thus, inputs J and K of the flip flop circuit 81 go to 1 when the stop push button 84 is opened.

When input C of the flip flop circuit 81 receives a negative going signal from terminal 8 of the terminal board 35 after J and K inputs of the flip flop circuit 81 are at 1 due to the stop push button 84 opening, outputs Q and Q change states. As previously mentioned, a negative going signal is supplied to terminal 8 of the terminal board 35 from the sensor head 51 through the sensor amplifier 50 whenever the drive shaft of the tufting machine is at its preset or selected position.

. The negative going signal is supplied from terminal 8 of the terminal board 35 through a resistor 124 and a capacitor 125 to provide a at input C of the flip flop circuit 81. A positive voltage is supplied from the lead 65 through a resistor 126, which has a capacitor 127, to prevent random high frequency noise from triggering flip flop circuit 81, and a diode 128 in parallel, to provide a 1 at input C when the drive shaft is not in its selected position. The diode 128 serves the function of preventing a large-positive voltage from appearing at the same input of flip flop circuit 81. This large positive voltage occurs when the sensor output goes positive bechine. However, outputs Q and Q of the flip flop circuit 81 are not affected by these signals to input C so as to change state unless inputs J and K are at 1. (This occurs only when the stop push button 84 is opened); then, the next 1 and 0 signals at input C of the flip flop circuit 81 will cause outputs Q and Q to change state when the 0 signal is received. Since output?) was at 1 and output Q was at 0 due to reset (RD) input of the flip flop circuit 81 receiving a 0 at the time of applying power to the tufting machine, output 6 goes to 0 and output Q goes to 1.

Since output Q of the flip flop circuit 81 is connected to input C of the flip'flop circuit 77, this results in a 0 being supplied to input C of the flip flop circuit 77. When this occurs, output Q of the flip flop circuit 77 goes to 0 and output 6 goes to 1. It should be understood than input K of the flip flop circuit 77 has remained at 1 from the time that power was supplied. Thus, when the flip flop circuit 81 wascleared due to 0 being supplied to reset (RD) input of the flip flop circuit 81 so that output 6 of the flip flop circuit 81 went to l, the information of input K being at l and input J being at 0 inthe flip flop circuit 77 was latched in the flip flop circuit 77. Therefore, when input C of the flip flop circuit 77 goes to 0, output Q of the flip flopcircuit 77 goes to 0 and output 6 of the flip flop circuit 77 goes to 1.

When output Q of the flip flop circuit 77 goes to 0,

- the input pin 91 of the NOR gate 92 also goes to 0 whereby the output pin 93 of the NOR gate 92 goes to 1 since the input pin 94 is at 0 due to the output pin 1 17 of the NAND gate 116 being at 1. The input pin 94 of the NOR gate 92 is connected to output pin 129 of NOR gate 130 through leads 131 and 132. Since the NOR gate 130 has its input pin 133 connected through a lead 134 to the output pin 117 of the NAND gate 116, the input pin 133 of the NOR gate 130 is at 1 whereby the output pin 129 is at 0.

- When the output pin 93 of the NOR gate 92 at 1, the output pin 98 of the NOR gate 97 goes toO. Since this signal is supplied by the lead 99 through the resistor 100 to the base of the transistor 46, the transistor 46 is turned off to deenergize the relay 39.

When this occurs, the contacts 39-1 of the relay 39 open and the control relay 25 is dropped. This results in the normally open contacts 25-1, 25-2 and 25-3 of thecontrol relay 25 opening and stopping the supply of power to the motors 20'and' 21.

When the relay 39 is deenergized, the contacts 39-2 return to their normally closed position. Accordingly, the relay 41 is capable of being energized when the transistor 47 is turned on.

The energization of the relay 41 results indynamic braking of the motors 20 and 21. It is desired for dynamic braking to occur three revolutions after the motors 20 and 21 have been disconnected from power to reduce the momentum before dynamic braking is applied. Accordingly, the flip flop circuits 79, 80 and 81 are connected to provide a 0 signal at the input pin 104 of the NOR gate 102 after three revolutions of the drive shaft following disconnection of the motors 20 and 21 from the power source.

When the input pin 104 of the NOR gate 102 goes to 0, the output pin 103 of the NOR gate 102 goes to 1 because the input pin 101 is already at 0 due to the output pin 98 of the NOR gate 97 going to 0 as soon 'as the first negative going signal from terminal 8 of the terminal board 35 is received at input C of the flip flop ircuit 81. This jO signal at input C of the flip flop circuit 81 is due to the first occurrence of the drive shaft at its selected position after the stop push button 84 is opened.

The flip flop circuit 81 has its output Q connected to input C of the flip flop circuit 80, which has its output Q connected to input C of the flip flop circuit 79. Accordingly, when the first O is received at input C of the flip flop circuit 81 after opening of the stop push button 84, output Q of the flip flop circuit 81 goes to 1. Thus, input C of the flip flop circuit 80 goes to 1.

With input C of the flip flop circuit 80 at 1, output Q of the flip flop circuit 80 remains at 0 because it changes state only when inputs J and K are at 1 and input C first'goes from 0 to 1 and then from 1 to 0. Therefore, when input C of the flip flop circuit 81 receives the first 0 signal after the stop push button 84 is opened, output Q of the flip flop circuit 80 remains at 0 so that output 6 of the flip flop circuit 79 remains at 1. Thus, only the relay 39 is deenergized due to the first negative going signal from terminal 8 of the terminal board 35.

When the drive shaft of the tufting machine completes one revolution after the motors 20 and 21 have been deenergized, a second 0 signal is received at input C of the flip flop circuit 81. The 1 signal was received between the 0 signals due to the connection of the lead to input C of the flip flop circuit 81 through the resistor 126. I

With the arrival of the second 0 signal at input C of the flip flop circuit 81 due to the drive shaft of the tufting machine completing one revolution, output- Q of the flip flop circuit 81 goes to from 1. As a result, output Q of the flip flop circuit 80 goes to 1 because input C changed from 0 to l and then from 1 to 0. When input C of the flip flop circuit 80 changes to 0, this changes the state of output Q.

Accordingly, input C of the flip flop circuit 79 goes from 0 to 1. When this occurs, the flip flop circuit 79 stores the information that input .l is at l and input K is at 0.

During the third 0 signal (second complete revolution of the drive shaft after disconnection of the motors and 21) to input C of the flip flop circuit 81 after the stop push button 84 was opened, output Q of the flip flop circuit 81 again goes to 1 so that input C of the flip flop circuit 80 changes from O to I. This again stores the information in the flip flop circuit 80 that inputs J and K are at l. However, output Q of the flip flop circuit 80 does not change state when input C goes to l but only when it goes to 0 after changing from 0 to 1. Therefore, input C of the flip flop circuit 79 remains at 1 during the third 0 signal at input C of the flipflop circuit 81. Thus, at the completion of two revolutions of the drive shaft of the tufting machine after disconnection of the motors 20 and 21 from the power source, output 6 of the flip flop circuit 79 remains at 1.

When the fourth 0 signal is received at input C of the flip flop circuit 31 due to the drive shaft of the tufting machine completing three revolutions, output Q of the flip flop circuit 81 again goes to 0 from 1. Accordingly, input C of the flip flop circuit 80 again goes to 0 so that output Q of the flip flop circuit 80 now changes state and goes from l to 0. This results in input C of the flip flop circuit 79 going from 1 to 0. When input C of the flip flop circuit 79 goes from 1 to 0 after having been changed from 0 to 1 previously, output 6 goes to 0 since input I of the flip flop circuit 79 is at l and input K of the flip flop circuit 79 is at 0. I Accordingly, output 6 of the flip flop circuit 79 cannot go to 0 until three revolutions of the drive shaft of the tufting machine have been completed following disconnection of the motors 20 and 21 from the power source. When output 6 of the flip flop circuit 79 goes to 0, the input pin 104 of the NOR gate 102 goes to 0 whereby the output pin 103 of the NOR gate 102 goes to 1 since the input pin 101 went to 0 when the first 0 signal is supplied to input C of the flip flop circuit 81 after the stop push button 8 4 is opened.

When the output pin 103 of the NOR gate 102 goes to l, the transistor 47 is turned on due to its base receiving a positive signal through the lead 105 and the resistor 106. Since the relay 39 was deenergized when the output pin 93 of the NOR gate 97 went to 0, the

The DC current is supplied from a bridge rectifier 138, which is connected to a secondary winding 138a of a transformer 1238b. The transformer 13% has its primary winding 138s connected to the leads 31 and 32.

A pilot light 139 is connected by a lead 139 so as to v be energized whenever the relay 135 is picked up.

Thus, the pilot light 139 provides a visual signal to the operator when the dynamic braking system is active.

In addition to being connected to the base of the transistor 47 to turn on the relay 41, the lead 105 also is connected through a lead 140 (see FIG. 2) to a timer circuit, which is employed to inactivate dynamic braking of the motors 20 and 21 after a selected period of time. The timer circuit includes a potentiometer 141 and a resistor 142 through which a capacitor 143 is charged when the output pin 103 of the NOR gate 102 goes to l. 5

The lead 140 also is connected to resistors 144 and 145, which cooperate to form a voltage divider connected through a lead 146 to the gate of a programmable unijunction transistor 147. The voltage divider of the resistors 144 and 145 brings the gate of the transistor 147 to a positive level of less than 5 volts.

As the capacitor 143 continues to charge, its voltage becomes slightly higher than the voltage at the gate of the transistor 147 whereby the transistor 147 conducts normally closed contacts 39-2 of the relay 39 are closed so that the relay 41 is picked up when the transistor 47 is turned on.

The energization of the relay 41 closes its normally open contacts 41-2 to connect terminal 4 of the terminal board to the lead 40 through the contacts 41-2 and normally closed contacts 39-3 of the control relay 39. The closing of the contact 41-2 of the relay 41 completes a circuit of an AC control relay 135 (see FIG. 1)

with the secondary winding 23 of the transformer 29 so that the-relay 133 is picked up.

When the relay 135 is activated, normally open contacts 135-1 and 135-2 of the relay 135 close. This allows DC current to be supplied to a winding of each of the motors 20 and 21 through leads 136 and 137.

heavily so as to discharge the capacitor 143 through a resistor 148 to ground. This rapid discharge of the capacitor 143 produces a momentary positive spike across the resistor 148. This spike is coupled through a diode 149 and the resistors 72 and 73 to the bases of the transistors and 71, respectively. This positive signal at the bases of the transistors 70 and 71 turns on the transistors 70 and 71 to again reset the entire logic through providing 0 signals on the leads 76 and 78.

When the 0 signal is supplied to reset (RD) input of the flip flop circuit 79, output Q again goes to 1 so that the input pin 104 of the NOR gate 102 is at l whereby the output pin 103 of the NOR gate 102 goes to 0. This turns off the transistor 47 and the relay 41 is dropped. The inactivation of the relay 41 opens the normally open contacts 41-2 so that the relay 135 is deenergized whereby its normally open contacts 135-1 and 135-2 open to stop the supply of DC current to the winding of each of the motors 21 and 21. This stops dynamic braking of the motors 20 and 21 with the drive shaft in its needles up position.

It should be understood that the 0 signal from the lead 76 is applied to the flip flop circuit 77 and the 0 signalfrom the lead 73 is applied to the flip flop circuits and 81 al the same time. However, the states of outputs Q and Q of the flip flop circuits 77 and 81 and the and the state of output Q of the flip flop circuit 80 are not changed since output Q of each of the flip flop circuits 77, 30 and 81 is already at 0 and output 6 of each of the flip flop circuits 77 and 81 is at l.

The amount of time that the dynamic braking is applied is controlled by the potentiometer 141. Thus, if the resistance of the potentiometer 14 is raised, this increases the time during which dynamic braking is applied since a higher resistance of the potentiometer 141 increases the time required to charge the capacitor 143 to a potential greater than that at the gate of the transistor 147. Similarly, reduction in the resistance of the potentiometer 141 decreases the time during which dy- I namic braking is applied.

The amount of time that the dynamic braking is applied in conjunction with the momentum at the time of the application of the dynamic braking determines the stopping position of the drive shaft. Thus, the rotary position of the piece of metal in the non-metallic disc on the drive shaft is selected in accordance with the time that the dynamic braking is applied so that the drive shaft is stopped in its needles up position.

Accordingly, when the stop push button 84 is opened, an automatic cycle occurs to stop the drive shaft of the tufting machine with its needles up and clear of the carpet. Furthermore, dynamic braking is applied for a selected period of time and is applied a predetermined period of time after the motors 20 and 21 are disconnected from the power source.

Furthermore, at the completion of the stop cycle, all of the flip flop circuits 77, 79, 80 and 81 are returned to their quiescent conditions. This is the same condition in which they are placed when the power is initially applied. I

If desired, the start pushbutton 82 can be closed at any time to begin another cycle as long as the stop push button 84 has been returned to its closed' position. If the start push button 82 is closed during a stop cycle with the stop push button 84 in its closed position, terminal 10' of the terminal board 35 is connected'to ground. 1

With terminal 10 of the terminal board 35 at ground, DC current can flow through the resistor 75, the lead 78, and a diode 150 to ground. The voltage drop across the resistor 78 provides a signal to reset (RD) input of each of the flip flop circuits 79, 80 and 81.

It is not necessary to supply a 0 signal to reset (RD) input of the flip flop circuit 77 at this time since a 0 signal from terminal of the terminal board 35 is supplied to set (SD) input of the flip flop circuit '77 when the start push button 82 is closed. Thus, the stop cycle can be interrupted by closing the start push button 82 if the stop push button 84 has been released and is in its closed position.

Whenever it is desired to move the drive shaft under control of the operator when the drive shaft is stopped, the jog push button 83 is closed. When this occurs, terminal 11 of the terminal board 35 is connected to ground through the closed stop push button 84 and terminal 9 of the terminal board 35. The 0 signal at terminal 11 of the terminal board 35 is applied through a filter network, which comprises an inductance 161 and capacitors 162 and 163, and a lead 164 to an input pin 165 of the NOR gate 130. v

Terminal 12 of the terminal board 35 also is at 0 because the stop push button 84 is closed. Accordingly, the input pin 107 of the NAND gate '108 is at 0 whereby the output pin 114 of the NAND gate 108 is at l and remains in this state as long as the stop push button 84 remains closed irrespective of the signal at the input pin 113 of the NAND gate 108. Therefore, the input pin 115 of the NAND gate 116 remains at 1 whenever the stop push button 84 is closed.

At the completion of a stop cycle or when power is initially turned on, the input pin 122 of the NAND gate 119 is at 0 whereby the output pin 121 of the NAND gate 119 goes to 1. This produces a 1 at the input pin 118 of the NAND gate 116 so that the output pin 117 of the NAND gate 116 goes to 0 since both of the input pins 115 and 118 are at l at this time.

With the output pin 117 of the NAND gate 116 at 0, the input pin 120 of the NAND. gate 119 goes tov 0. Therefore, even though the input pin 122 goes to l shortly after the stop cycle is completed or after power is initially turned on because of the transistor 71 ceasing to conduct, the output pin 121 of the NAND gate 119 does not change state and remains at 1 so that the output pin 117 of the NAND gate 116 remains at 0.

Thus, the input pin 133 of the NOR gate goes to 0 at the completion of a stop cycle or when power is initially applied because the input pin 133 is connected by the lead 134 to the output pin 117 of the NAND gate 116. Therefore, when the jog push button 83 is closed, both of the input pins 133 and are at 0 so that the output pin 129 of the NOR gate 130 goes to l. Accordingly, an input pin of a NAND gate 171 goes to 1 since it is connected to the output pin 129 of the NOR gate 130 by the lead 132.

The NAND gate 171 has its other input pin 173 connected by a lead 7410 output Q of the flip flop circuit 77. Since output Q of the flip flop circuit 77 is at 1 due to a 0 signal being suppliedto reset (RD) input of the flip flop circuit 77- at the completion of the stop cycle or when power is initially applied, the inputpin. 173 of the NAND gate 171 is at 1. Thus, output pin 175. of the NAND gate 171 goes to 0 since both of the input pins 170 and 173 are at l.

The output pin of the NAND gate 171 is connected to set (SD) input of the flip flop circuit 79 by a lead 176. Accordingly, when set (SD) input of the flip flop circuit 79 receives a 0 from the NAND gate 171 due to the jog push button 83 being closed, output 6 of the flip flop circuit 79 goes to 0 irrespective of the states of inputs .1 and K of the flip flop circuit 79. Thus,

the input pin .104 of the NORigate 102 goes to O.

The input pin 94 of the NOR gate 92 goes to 1 .when the jog push button 83 is closed sincethe input pin 94 is connected to the output pin 129 of the NOR gate 130 by the lead 131 and the lead 132. With the input pin 94 of the NOR gate being at l, the output pin 93 of the NOR gate 92 goes to 0. As a result, the input pins 95 and 96 of the NOR gate 97 go to 0 so that the output pin 98 of the NOR ga'te'97 goes to l.

Since the output pin 98 of the NOR gate 97 is connected by the lead 99 and the resistor 100 to the base of thetransistor 46, the transistor 46 turns on when the output pin 98 goes to 1 so as to pick the relay 39 since the relay 41 is inactivated at this time. This closes the normally open contacts 39-1 so that the control relay 25 is picked to cause its normally open contacts 25-1, 25-2, and 25-3 to close. Accordingly, the motors 20 and 21 are turned on when the jog push button 83 is closed.

The output pin 98 of the NOR gate 97 also is connected tothe input pin 101 of the NOR gate 102 by the lead 99. Accordingly, when the input pin 101 of the NOR gate 102 goes to l, the output pin 103 of the NOR gate 102 goes to 0 to insure that the transistor 47 is not turned on.

As soon as the jog push button 83 is released, terminal 11 of the terminal board 35 is no longer connected to ground so that the positive signal from the lead 65 is supplied through a resistor 178 to the lead 164 whereby the input pin 165 of the NOR gate 130 goes to 1. This causes the output pin 129 of the NOR gate 130 to go to 0 so that the input pin 94 of the NOR gate 92 also goes to 0.

When the input pin 91 of the NOR gate 92 already at because output Q of the flip flop circuit 77 has remainedat 0 since reset (RD) input received the 0 signal at the end of the stop cycle or when power was initially applied, both of the inputs to the NOR gate 92 are at 0 whereby its output pin 93 goes to 1. This causes the output pin 98 of the NOR gate 97 to change to 0 since its input pins 95 and 96 have changed to 1.

When the output pin 98 of the NOR gate 97 goes to 0, the transistor 46 ceases to conduct and the relay 39 is turned off. This drops the relay so that the contacts 25-1, 25-2 and 25-3 of the relay 25 open to stop rotation of the motors 20 and 21.

Since the output pin 98 goes to 0 when the jog button 83 is released, the input pin 101 of the NOR gate 102 also goes to .0. Since the input pin 104' of the NOR gate 102 went to 0 upon closing of the jog push button 83, the NOR gate 102 has both of its input pins 101 and 104 at 0. This causes the output pin 103 of the NOR gate 102 to go to 1. The transistor 47 is now truned on due to receiving a positive signal at its base through the lead 105 and the resistor 106.

Of course, the relay 41 cannot be energized even though the transistor 47 is turned on until the relay 39 is dropped since the normally closed contacts 39-2 of the relay 39 must again close. This insures that the relay 41 is not activated until the relay 39 is dropped.

The energization of the relay 41 closes the normally open contacts 41-2 so that the control relay 135 is energized. This closes the normally open contacts 135-1 and 135-2 of the relay 135 so that DC current is applied through the leads 136 and 137 to the winding of each of the motors 20 and 21.

In the same manner as previously described for the stop cycle, the positive signal from the output pin 103 of the NOR gate 102 also is supplied through the lead 140 to the timer circuit. The timer circuit again deenergizes the relay 41 a predetermined period of time after the relay 41 is picked up in accordance with the magnitude of the resistance of the potentiometer 141. Thus, when the relay 41 is turned off by the timer circuit,,the flip flop circuits 77, 79, 80 and 81 are again reset by the timer circuit since both of the transistors 70 and 71 are turned on momentarily.

The relay 39 has a diode 179 in parallel .therewith, and the relay 41 has a diode 180 in parallel therewith. The purpose of these diodes 179 and 190 is to prevent transient cuttents from flowing in the transistors 46 and 47 when the relays 39 and 41 are deenergized.

The NOR gates 92, 97, 102 and 130 preferably comprise a single integrated circuit sold as Model US 7402 by Sprague. However, any other suitable NOR gates may be employed.

The NAND gates 108, 116, 119 and 171 preferably comprise a single integrated circuit sold by Sprague as Model US 7400. However, any other suitable NAND gates may be employed.

When the flip flop circuits 77 and 79 are a single integrated circuit, the flip flop circuits 80 and 81 are a single integrated circuit, the NOR gates 92, 98, 102 and 130 are a single integrated circuit, and the NAND gates 108, 116, 119 and 171 are a single circuit, DC power to these integrated circuits is supplied from the lead 65 through a lead 181. The wiring diagram of FIG. 2 has shown these elements as parts of integrated circuits.

The control circuit of the present invention enables the start push button 82 to be closed at any time, even 14 during a stop cycle, to startthe machine unless the stop push button 84 is open. If the stop push button 84 is open, the machine not only is incapable of being started but it also cannot be jogged since each of these requires the stop push button 84 to be closed.

One example of the various parameters of the circuit of the present invention follows:

Transistors 46 and 47 General Electric 2N34l7 70 and 71 General Electric 2N3393 147 General Electric 2N6027 Resistors in Ohms 74, 75, 89, 100, 106, 109, 126, and

lnductances in Millihenries as, 110 and 161 2.5'

Capacitors in Microfarads 49 and 61 250 66 500 67 and 143 10 86, 87,111, 112, 125, 127, 162 and Diodes General Electric INSO60 General Electric lN4l48 48 and 60 128, 149, 150, 179 and 180 While the control circuit of the present invention has been shown and described as being employed to control the motor of a tutting machine, it should be understood that the control circuit of the present invention may be utilized with any AC motor having a constant load. Thus, the circuit may be utilized whenever it is desired to stop a shaft of an AC motor with a constant load at a predetermined position. While the control circuit of the present invention has been shown and described as being employed with two motors, it should be understood that the control circuit may be utilized to control one motor or more than two motors if desired.

An advantage of this invention is that it does not use a mechanical braking device. Another advantage. of this invention is that there are no moving parts in the braking arrangement. A further advantage of this invention is that no clutch is required.

For purposes of exemplification, a particular embodiment of the invention has been shown and described according to the best present understanding thereof. However, it will be apparent that changes and modifications in the arrangement and construction of the parts thereof may be resorted to without departing from the spirit and scope of this invention.

What is claimed is:

1. A device for automatically stopping an AC motor having a constant load at a predetermined rotary position including means to sense when the motor is at a selected rotary position, means to produce a signal when it is desired to stop the motor, means to disconnect the motor from its AC power source'in response to a signal from said producing means and said sensing means sensing that the motor is at the selected rotary position, means to apply a DC voltage to the motor a predetermined period of time after said disconnecting means is effective to dynamically brake the motor so that the motor stops at the predetermined rotary position, means to control said applying means to prevent said applying means from being effective until'the motor has made a predetermined number of revolutions after said sensing means is effective, means to inactivate said applying means after a selected period of time, means to vary the selected period of time and means to start the motor, said starting means being effective to start the motor even 'after said disconnecting means has become effective.

2. A device for automatically stopping an AC motor having a constant load at a predetermined rotary position including means to sense when the motor is at a selected rotary position, means to produce a signal when it is desired to stop the motor, means to disconnect the motor from its AC power source in response to a signal from said producing means and said sensing means sensing that the motor is at the selected rotary position, means to apply a DC voltage to the motor a predetermined period of time after said disconnecting means is effective to dynamically brake the motor so that the means to control said applying means to prevent said applying means from being effective until the motor has made a predetermined number of revolutions after said sensing means is effective, said control means including means to count each revolution of the motor.

3. A device for automatically stopping an AC motor having a constant load at a predetermined rotary posi tion including means to sense when the motor is at a selected rotary position, means to produce a signal when it is desired to stop the motor, means to disconnect the motor from its AC power source in response to a signal from said producing means and said sensing means sensing that the motor is at the selected rotary position, means to apply a DC voltage to the motor a predetermined period of time after said disconnecting means is effective to dynamically brake the motor so that the motor stops at the predetermined rotary position, means to control said applying means to prevent said applying means from being effective until the motor hasmade a predetermined number of revolutions after said sensing means is effective, said control means including means to count each revolution to the motor, and means to inactivate said applying means after a selected period of time.

i it II I I 

1. A device for automatically stopping an AC motor having a constant load at a predetermined rotary position including means to sense when the motor is at a selected rotary position, means to produce a signal when it is desired to stop the motor, means to disconnect the motor from its AC power source in response to a signal from said producing means and said sensing means sensing that the motor is at the selected rotary position, means to apply a DC voltage to the motor a predetermined period of time after said disconnecting means is effective to dynamically brake the motor so that the motor stops at the predetermined rotary position, means to control said applying means to prevent said applying means from being effective until the motor has made a predetermined number of revolutions after said sensing means is effective, means to inactivate said applying means after a selected period of time, means to vary the selected period of time and means to start the motor, said starting means being effective to start the motor even after said disconnecting means has become effective.
 2. A device for automatically stopping an AC motor having a constant load at a predetermined rotary position including means to sense when the motor is at a selected rotary position, means to prOduce a signal when it is desired to stop the motor, means to disconnect the motor from its AC power source in response to a signal from said producing means and said sensing means sensing that the motor is at the selected rotary position, means to apply a DC voltage to the motor a predetermined period of time after said disconnecting means is effective to dynamically brake the motor so that the motor stops at the predetermined rotary position and means to control said applying means to prevent said applying means from being effective until the motor has made a predetermined number of revolutions after said sensing means is effective, said control means including means to count each revolution of the motor.
 3. A device for automatically stopping an AC motor having a constant load at a predetermined rotary position including means to sense when the motor is at a selected rotary position, means to produce a signal when it is desired to stop the motor, means to disconnect the motor from its AC power source in response to a signal from said producing means and said sensing means sensing that the motor is at the selected rotary position, means to apply a DC voltage to the motor a predetermined period of time after said disconnecting means is effective to dynamically brake the motor so that the motor stops at the predetermined rotary position, means to control said applying means to prevent said applying means from being effective until the motor has made a predetermined number of revolutions after said sensing means is effective, said control means including means to count each revolution to the motor, and means to inactivate said applying means after a selected period of time. 